Cable with weakened stripping plane



Jan. 20, 1953 T. K. cox

CABLE WITH WEAKENED STRIPPING PLANE Filed Sept. 9, 1947 FIG. 2

A TTORNEY Patented Jan. 20, 1953 CABLE WITH WEAKENED STRIPPING PLANEThomas K. Cox, Randallstown, Md., assignor to Western Electric Company,Incorporated, New York, N. Y., a corporation of New York ApplicationSeptember 9, 1947, Serial No. 773,005 (01. 174-113) .3 Claims.

This invention relates to electrical cables, and more particularly toelectrical cables with weak- ,ened'stripping planes.

In the use of electrical cables of a type which includes a plurality ofindividually insulated conductors twisted together and enclosed in atough weatherproofing jacket, it is often necessary to remove endportions of the jacket of such a jacketed conductor in order to connectthe individually insulated conductors thereof to electrical apparatus.Such removal of the jacket, which is formed of very tough material, isdifficult.

An object of the invention is to provide new and improved electricalcables.

A further object of the invention is to provide a multi-conductor cablehaving a packet therearound which is provided with a weakened portionextending along one of the conductors.

An electrical cable illustrative of certain features of the inventionincludes a plurality of individually insulated, bunched conductors, anda jacket enclosing the conductors and having a weakened stripping planeextending along one of said conductors.

A complete understanding of the invention may be obtained from thefollowing detailed description of a cable embodying the invention, whenread in conjunction with the appended drawings, in which:

Fig. 1 is a fragmentary, sectional view of an apparatus for performingsome of the operations used in making the cable;

Fig. 2 is a front elevation of an apparatus for performing anotheroperation used in making the cable, and

Fig. 3 is an enlarged, vertical section taken along line 3-3 of Fig. 2.

Referring now in detail to the drawings, individually insulatedconductors Ill, H and 12, which include solid conductors l4, l5 and I6,respectively, and colored coverings ll, I8 and :9, respectively, each ofwhich coverings is of a color different from that of the othercoverings, are advanced through an extruder 22 in parallel, spacedrelationship together with Fiberglas strands 23-23 (Fig. 3), and theextruder forms a jacket 24 around the individually insulated conductorsand the strands to form a jacketed cable 25. The jacket 24 is composedof a jacketing compound including a thermoplastic material, such as acopolymer of vinyl chloride and vinyl acetate, and as it is formedaround the individually insulated conductors and the strands 23 23*, aknife 26 projecting from a die 21 forms a slit 28 in the jacket alongthe conductor l I. The

' 2 portion of the die beyond the knife closes the slit while thematerial is still somewhat plastic so that a smooth exterior surface isimparted to the jacket.

The molecules of the portions of the jacket on each side of the slit areoriented by the knife so that they extend lengthwise with respect to theconductor, and the rescaled portions of the jacket form a cleavage planealong which the jacket has its least tear resistance. However, the tearresistance of the jacket alon the cleavage plane is sufliciently high towithstand all the stresses ordinarily encountered in the normal use ofthe jacketed conductor 25. Thus, the tear resistance of the portion ofthe jacket'along the cleavage plane is lowest without decreasing theabrasion resistance of this portion of the jacket since the slit isrescaled and the exterior surface of the jacket is completely smooth.

The jacketed cable 25 then is advanced from the extruder into andthrorgh a cooling trough 30, into which cold water is introduced, whichcools the jacket 24. Although the slit 28 is closed and the ides thereofare sealed together, the jacket is substantially weaker along the slit28 than it is at any other portion thereof, and the color of thecovering I8 adjacent to the slit 28 locates the slit for strippingoperations of the jacket during installation of the jacketed cable.

After the jacket 24 has been formed over the three conductors [0, H andI2, the jacketed cable 25 is placed on a revolving supply unit 34 of atwister 32 (Fig. 2) which also includes a takeup capstan 36 and a takeupreel 31. The supply unit twists the cable as the takeup capstan 36advances it therefrom through a guide 38. This twisting twists theindividually insulated conductors Ill, H and i2 together so that thecable will have the proper electrical characteristics and flexibility.The twister 32 serves to twist the solid conductors I4, 15 and I6suiiiciently beyond their elastic limits to cause these conductors tohold the entire cable in its twisted form.

While the outer surface of the jacket 24 is completely smooth andunmarked, it has a cleavage plane along the insulated conductor I lwhere the slit 28 was formed, Thus, the coloring of the covering l8 ofthe insulated conductor H locates the weakened portion of the jacket sothat the end portions of the jacket may be easily stripped from the endportions of the individually insulated conductors [0, II and I2,Although the tear resistance of the jacket 24 is weakened somewhat alongthe cleavage plane, this portion of the jacket has suiiicient strengthto withstand 3 ordinary usage of the jacketed conductor. and iscompletely watertight.

If it is wished to form the jacket 24 from a thermosetting type ofplastic, such as rubber compound or a compound containing a synthetic,rubber-like material, the above-described method may be used ifvulcanization is substituted for the step of cooling the jacket after ithas been extruded. Furthermore, other thermoplastic materials, as wellas thermosetting materials, may be used in place of the co-polymer ofvinyl chloride and vinyl acetate. For example, polymerized ethylene,polymerized isobutylene or polymerized vinyl chloride may be used inplace of the co-poly mer of vinyl chloride and vinyl acetate. J acketedcables having either more or less than three individually insulatedconductors may be formed by the above-described method.

What is claimed is:

1. An electrical cable, which comprises a plurality of individuallyinsulated, bunched-together conductors, and an outermost jacketenclosing the conductors and having a weakened, sealed portion extendingalong one of said conductors and extending radially toward said one ofsaid conductors from the exterior of said jacket.

2. An electrical cable, which comprises a plurality of individuallyinsulated conductors, each of said conductors having a covering of acoloring diiferent from those of the others, and an outside jacketcomposed of thermoplastic compound enclosing the conductors and havingan invisible, sealed cleavage plane extending radially along one of theconductors, whereby the invisible cleavage plane of the jacket may belocated 35 4 at the conductor end by a color of the covering of thatconductor.

3. An electrical cable, which comprises at least three individuallyinsulated conductors, and an outside tight-fitting jacket composed ofthermoplastic compound enclosing the conductors, said jacket and saidconductors being twisted to a predetermined pitch along substantiallythe entire length thereof, said jacket being integral throughout andhaving a weakened portion extending along one of said conductors andextending radially inwardly toward said one of said conductors from theexterior of the jacket.

THOMAS K. COX.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 170,266 Hoogeveen Nov. 23, 18751,627,740 Hosford May 10, 1927 1,940,917 Okazaki Dec. 26, 1933 2,106,048Candy Jan. 18, 1938 2,204,782 Wermine June 18, 1940 2,232,085 TrocheFeb. 18, 1941 2,413,715 Kemp et al Jan. 7, 1947 FOREIGN PATENTS NumberCountry Date 530,297 England Dec. 9, 1940 544,427 England Apr. 13, 1942681,220 Germany Sept. 18, 1939

